Conduits which are used to convey a fluid underwater are typically used in industry. For example, such conduits may be utilized as discharge pipes for waste water treatment plants wherein waste water is conveyed through the conduit, under water, to a discharge location which is distal to the shore. Other such underwater conduits include intakes and transmission pipelines that may transport process, drinking or cooling water.
Typically, underwater conduits are prepared by securing lengths of pipe together, such as by means of an external clamp, flanges, bell and spigot fittings, mechanical couplers, welding or mating of threaded ends, which forms a joint connecting two adjacent pipes. In all such cases, the end of one pipe is positioned adjacent the beginning of the next pipe. The external clamp or the like is utilized to secure the two ends together and to create a water-tight seal between the two adjacent pipes. Accordingly, once assembled, fluid (e.g. waste water or the like) may be conveyed through the conduit without the waste water exiting the conduit via a joint or, alternately, water will not seep into the pipe from the body of water through which the pipe passes.
Over time, leaks may develop in an underwater conduit. For example, the lake bed, river bed or ocean floor in which the conduit is placed may settle resulting in stress on the clamp or the like which secures the ends of two pipes together. This stress may result in the relative movement of one pipe compared to the adjacent pipe thereby producing a gap through which fluid may leak. Alternately, one or more of the pipes and the clamp or the like may deteriorate producing a gap or crack through which fluid may leak.
When a leak occurs, then corrective steps may be taken. For example, a liner may be installed in the conduit. Alternately, spot repair liners may be installed to cover the joints where two pipes connect. Such liners are designed to create a water tight seal between the exterior surface of the spot repair liner and the interior surface of the conduit thus creating a continuous water tight surface which bridges the portion of the conduit in which the leak has occurred. However, the efficacy of spot liners is based on many factors including pipe diameter and the backing material. Accordingly, in some applications, spot repair liners are not desirable.
An alternate method for sealing a gap comprises applying a new cement coating to the inside of the pipe. Such a coating may be applied by various techniques known in the art including pneumatically (shot-crete), or hydraulically (spun in place) or by slip-forming.
Various types of concrete compositions are known. Further, it is known to add fibres to cement to increase the flexural and tensile strength of the cured product (Nagler Jr. et al, United States Patent Publication No. 2005/0056190). As disclosed by Nagler et al, an aqueous gel solution is formed from water and a thickener. Fibres are then added to the gel solution. Subsequently, the gel composition containing the fibres is combined with a cement composition. Nagler et al discloses a large variety of thickeners including psyllium.